Lamp base assembly



Oct. 23, 1962 B sc oL s 3,060,344

LAMP BASE ASSEMBLY Filed Feb. 17, 1960 /wm E 22 INVENTOR. ADD/SON B. SCI-/OLES lal W m ATTOR NE YS 3,060,344 LAMP BASE ASSEMBLY Addison B. Scholes, Warren, Pa., assignor to Cersolsun Research Corporation, Warren, Pa., a corporation of Delaware Filed Feb. 17, 1960, Ser. No. 9,214 Claims. (Cl. 315-58) This invention relates to a lamp base assembly and, more particularly, it relates to a lamp base assembly having a current-limiting resistance device as a part thereof.

Current-limiting resistance devices or resistors are required for satisfactory operation of the lamps in many types of electrical lamps. Although resistors may be used in certain incandescent lamps where the lamp filaments must be protected from damaging high voltages, resistors are generally employed in gaseous discharge lamps where they are required to properly control the electrode current for lamp operation.

Current-limiting resistors may be incorporated either directly in the base of the la-mp itself or the resistor may be positioned in the circuit outside of the lamp. Placement of the resistor in the lamp base is generally preferred, but such placement may create a number of problems. For example, one of the primary problems is the space required -for placement of a suitable resistor in the lamp base, and this is particularly important when miniature lamps are being produced. As a result, lamp designs have been suggested in which a portion of the base is enlarged to form a so-called skirt which provides space for a resistor.

Another problem encountered When the resistor is to be positioned in the lamp base is the assembly of the resistor within the close confines of the base, that is, the connecting of the resistor to the electrode leads by soldering or the like.

P ositioning of a current-limiting resistor in a lamp base also requires that the resistor have a somewhat larger rated capacity than may be required so that the proper resistance value may be attained in spite of the drop in actual resistance at the elevated temperatures occurring in the base during lamp operation.

The lamp base assembly of the present -invention overcomes many of the difiiculties encountered in previous constructions. For example, provision is made for the easy and quick assembly of the resistor in the lamp base and the resistor may be connected to the lamp leads simply and Conveniently. Furthermore, no enlargement of the lamp base is required for receiving of the resistor. Moreover, in low amperage lamps, the lamp lead connections with the circuit elements of the lamp base may be simple pressure contacts without the necessity of soldering, welding or similar methods.

Other features and advantages of the invention will be apparent from the following detailed description and the drawing in which:

FIGURE 1 i-s a :partially sectioned side elevation of a lamp embodying the present invention.

FIGURE 2 is an enlarged sectional View of a portion of the base assembly shown in FIGURE 1.

FIGURE 3 is a sectional view of the portion of the base assembly shown in FIGURE 2 taken along line 3-3 of FIGURE 2.

FIGURE 4 is a greatly enlarged sectional view taken through the axis of the cylindrical current-limiting resistor which is employed in the base assembly shown in FIG- URE 1.

As shown in FIGURE l, an electrical lamp is provided with a glass bulb or envelope 11 and a suitable base assembly for securing the lamp in a suitable receptacle or ic taes rent socket. The base assembly includes a metallic shell 13 which is afixed to the glass bulb 11 with a suitable basing cement 12. The metallic shell 13 may have a threaded portion 14 for securing the lamp in a socket and which engages a circuit contact located in the socket. An insulating member 15 is carried by metal shell 13 and preferably the insulating member has a central opening in which is positioned a resistor 16 which serves as a bottom contact button -for the lamp and engages a second circuit contact of the socket.

The glass bulb 11 has a pair of suitable electrode leads 18 and 19, the lower ends of which project through the end wall of the bulb 11 and extend into pressure contact, respectively with circuit elements of the 'base assembly so as to form an electrically conductve circuit through the lamp. The lower end of lead 18 is in contact with the metal shell 13 serving as one of these circuit elements, and the lower end of lead 19 is in contact with the resistor 16 serving as the other of these circuit elements.

The insulating member 15 may be of any appropriate shape so long as the resistor 16 may be secured theren in a position which permits a substantial portion of the resistor to extend outwardly therefrom. Advantageously, as shown in FIGURES 3 and 4, the insulating member 15 has a lower shoulder portion 21 and an upper portion 22, preferably polygonal, to facilitate the securing of the insulator 15 in the metal shell 13` such as by a press fit. An aXial -bore through the insulator receives one end of the resistor.

The insulating member 15 may be made of any of the nonconductive or dielectric materials considered suitable in the electrical industry. Advantageously, the insulating member 1'5 is made of a plastic material which is deformable to some extent so that a secure assembly of the Components may be made without fracturing the insulating member. Examples of suitable plastics include nylon, polyethylene, polytetrafluoroethylene, `and sinilar materials.

The resistor 16 shown in detal in FIGURE 4 may -be made of an appropriate semi-conductve material which provides the desired degree of resistance. Advantageously, the resistor has a central core portion 24 surroundedi by a refractory insulating portion or covering 25. The semi-conductve core 24 may be made of a carbonaceous material such as a bonded carbon or graphite, and preferably is a clay-bonded graphite. The outer portion 25 may be of any desired insulating material preferably a ceramic porcelain or the like.

When the resistor is made of a clay-bonded graphite, the outer insulating portion may be 'formed as an integral part of the resistor as indicated by the continuity of the cross-hatching of the body of the resistor with light and heavy lines respectively representing the semi-conductve core and the surrounding insulating portion. For example, the clay-bonded graphite may be pressed into an appropriate shape and the pressed article then placed in an oven and baked in a controlled oxidzing atmosphere.

This baking step causes the graphite close to the outer surface of the pressed article to be removed by oxidation with the result that the clay is sintered forming -an outer insulating wall around the bonded graphite core.

To facilitate the forming of proper electrically conductive contacts between the upper and lower surfaces of the resistor and the lamp lead and socket, respectively, without soldering, welding, or the like, the top and bottom surfaces 26 and 27 of the resistor 16 are advantageously coated with a highly conductve metal such as copper. Preferably, the metal coating is formed by spraying or electroplating so that the c-oating will be tightly adherent to the surface of the resistor and will not flake ofI".

The metallic shell 13 has its lower end turned inwardly and upwardly so as to form an internal, axially inwardly opening annular channel for gripping the insulator 15 while holding it spaced from the interior of the shell beyond the channel. This channel obviously rigidifies the shell 13 to better resist distortion of the shell to an outof-round condition when the polygonal portion 21 of the insulator 15 is forced therein with the aforementioned press fit. Also, as shown, this channel maintains an annular pocket about the portion 21 of the insulator for receiving the projecting lower end of the lamp lead 18, and provides a conductive surface at the bottom of the pocket which this lead may engage with the aforementioned pressure contact so as to eliminate any need for a soldered or welded connection at this point. The central bore of the insulator 15, with the resistor 16 projecting only partially theret hrough and the upper conductive sur- `face 26 of the resistor exposed therein, provide another pocket and a highly conductive pressure contact surface at the bottom thereof for the other lamp lead 19. This similarly eliminates any need for a soldered or -welded connection between the lead 19 and the resistor.

As pointed out above, current-limiting resistors are generally employed in connection with gaseous discharge lamps, one type of which is the glow lamp. Illumination is achieved in a glow lamp when current of the required voltage passes between the electrodes of the lamp causing the gas therein to glow. Suitable inert gases are helium, -argon, neon, krypton and other noble gases or mixtures thereof. A fluorescent glow lamp may be made by coating the interior of the glass bulb of the lamp with a phosphor coating which will `be excited by the gas in the lamp.

In addition to applications in which glow lamps are employed for the purpose of illumination, lamps of this type may be used in electrical circuits as indicators and also may be used as voltage control devices in switches and circuit breakers. Generally, in these uses, the lamps do not have a phosphor coating on the inside of the lamp envelope.

As shown in the foregoing description, the present invention provides a lamp base assembly which overcomes many of the difficulties encountered in previous constructions. The lamp base assembly of the invention provides for the easy and quick assembly of a current-limiting resistor in the base of a lamp without requiring the enlargement of the lamp base. Also, the resistor may be connected to the lamp leads simply and Conveniently and in low amperage lamps the connections may be made without the necessity of soldering, welding or similar methods. In addition, the lamp base assembly of the invention may be produced at a cost which is substantially lower than that of previously known resistor-containing base assemblies.

It is apparent from the above description that various modifications within the scope of the invention may be made in the lamp base assembly described. Therefore, it is not intended that the invention be limited to the particular lamp base assembly disclosed in detal herein except as may be required by the appended claims.

What is claimed is:

1. A lamp base assembly for a gaseous discharge lamp comprising at least two electrically conductive circuit elements separated by a dielectric material, one of said circuit elements being a metallic shell for engaging one circuit contact of a lamp socket and another of said circuit elements being a current limiting resistor at least partially received within said shell, said resistor being laterally surrounded by said dielectric material and having an electrically conductive end portion thereof facing outwardly and exposed 'for engagng a second circuit contact of said lamp socket.

2. A lamp base assembly according to claim 1 in which said metallic shell has an upper opening for receiving a glass lamp envelope and a lower opening in which an insulating member is received to provide the dielectric separation of said circuit elements.

3. A lamp base assembly according to claim 1 in which said metallic shell has an upper opening for receiving a glass lamp envelope and a lower opening in which an insulating member is received to provide the dielectric separation of said circuit elements, said insulating member being made of a deformable material and being received and 'held in said shell with a press fit.

4. A lamp base assembly according to claim 1 in which said metallic shell has an upper opening for receiving a glass lamp envelope and a lower opening in which an insulating member is received to provide the dielectric separation of said circuit elements, and said insulating member has a generally axially extending bore in which said resistor is received.

5. A lamp base assembly according to claim 1 in which said resistor has an inner electrically conductive end portion exposed for pressure electrical contact with a lamp electrode lead.

6. A lamp base assembly according to claim 1 in which said resistor comprises a carbonaceous core laterally surrounded by said insulating material, including an outer insulating layer integrally formed with said core, said outwardly facing end of the core and an inwardly exposed end thereof having coatings of highly conductive metal thereon to provide contact surfaces for said second lamp socket contact and for a lamp electrode lead, respectively.

7. A lamp base assembly for a gaseous discharge lamp comprising at least two separated electrically conductive circuit elements, one of said circuit elements being au annular metallic shell for engaging one circuit contact of a lamp socket and having an opening at one end for receiving a glass lamp envelope and at least two electrode leads from said envelope, and having an opening at its opposite end for receiving the other of said circuit elements, nsulation material being received and held in said opposite end of said metallic shell and laterally surrounding .and supporting said other circuit element spaced from said metallic shell, and said other circuit element being a current limting resistor having an electrically conductive end portion facing outwardly and exposed for engaging a second circuit contact of a lamp socket and having an opposite electrically conductive end portion facing inwardly and exposed for engaging one of said lamp electrode leads, said metallic shell having an inner exposed surface for engaging the other of said lamp electrode leads.

8. A lamp base assembly according to claim 7 in which said nsulation material is a deformable body held in said metallic shell with a press fit and having a bore extending therethrough for receiving and supporting said resistor therein.

9. A lamp base assembly according to claim 7 in which said opposite end of said metallic shell is turned inwardly and axially to form an axially inwardly opening annular channel surrounding said insulating material and holding it spaced from the interior of the shell beyond the channel to form a pocket for receiving said other of said lamp electrode leads and forming said inner exposed surface of the shell at the bottom of the pocket for pressure engagement by said other of said lamp electrode leads.

10. A lamp base assembly according to claim 7 in which said opposite end of said metallic shell is turned inwardly and axially to form an axially inwardly opening annular channel surrounding said insulating material and holding it spaced from the interior of the shell beyond the channel to form a pocket for receiving said other of said lamp electrode leads and forming said inner exposed surface of the shell at the bottom of the pocket for pressure engagement by said other of said lamp electrode leads, and said nsulation material is a deformable body having a bore extending therethrough and having a press fit in the channel-forming portion of said shell, said resistor being received and supported in said bore with its inwardly facing end portion stopping short of the inner 5 end of the bore, whereby said bore also forms a pocket for receiving said one of said lamp electrode leads in pressure engagement with said inwardly facing end portion of the resstor.

References Cited in the file of this patent UNITED STATES PATENTS %30,477 Forster Sept. 4, 1906 6 Triquet June 10, 1913 Van Voorh's Jan. 18, 1927 Conradty May 26, 1931 Moore July 28, 1931 Stoflel June 9, 1942 Boardman Aug. 24, 1943 FOREIGN PATENTS Great Britain June 6, 1951 

